1. Field of the Invention
This invention relates to a fault compensation method for an air conditioner which is used when position setting contacts of an actuator for driving a mode switch door malfunction or when abnormality occurs in a control unit of the actuator and to a fault compensation apparatus for an air conditioner.
2. Description of the Prior Art
Generally speaking, an air conditioner ejects air whose temperature has been adjusted to an appropriate temperature by an air mix door from a ventilation air outlet at a downstream of a duct, a foot air outlet, a defrost air outlet and the like. In this case, a mode switch door is located at a downstream of the duct and controlled by an actuator. Its control modes are, for example, defrost, defrost/foot, foot, bilevel and ventilation modes. These modes are switched by a mode changing switch.
FIG. 12 shows an example of an actuator control system for controlling the above mode switch door disclosed in JP-A-63-2716 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), for example. In the figure, reference numeral 1 represents a control unit which has a microcomputer 2. A drive circuit 3 formed of a circuit for controlling normal and reverse rotations of a motor is controlled by the output of this microcomputer 2 and the output of the drive circuit 3 is supplied to a motor 5 which constitutes an actuator 4 for controlling a mode switch door.
Reference numeral 6 represents a mode changing switch which is provided on an air conditioner operation panel located near the dashboard of a car and which consists of a defrost switch 7, a defrost/foot switch 8, a foot switch 9, a bilevel switch 10 and ventilation switch 11. A mode setting signal corresponding to each of the switches 7 to 11 is applied to the microcomputer 2.
The above actuator 4, as shown in FIG. 11, controls the opening of the mode switch door 13 through a link unit or a gear unit 12. The mode switch door 13 consists of a door 13a for adjusting the amount of air blowing out from the foot air outlet F at a downstream of the duct and a door 13b for controlling the amount of air blowing out from upper and lower branch ducts D1 and D2 provided at an upper position of the downstream of the duct. In FIG. 11, MD represents an air mix door.
In FIG. 12, a setting unit 19 which comprises a ventilation mode setting contact 14, a bilevel mode setting contact 15, a foot mode setting contact 16, a defrost/foot mode setting contact 17 and a defrost mode setting contact 18 is provided in a casing constituting the actuator 4. As shown in FIG. 13, the contacts 14 to 18 are provided on an unshown output plain gear of the motor 5, for example, and formed by a movable contact 20 which rotates together with the output plain gear and fixed contacts 21 which are provided on the inside surface of the casing which faces the output plain gear. When the output gear turns with the rotation of the motor, the movable contact 20 also rotates and contacts one of the fixed contacts 21 to turn on the contact. Output from each of the contacts 14 to 18 is input into the microcomputer 2 through the input circuit 22. The fixed contact 21 of the above ventilation mode setting contact 14 corresponds to a position when the mode switch door 13 driven by the actuator is set to a ventilation mode, the fixed contact 21 of the bilevel mode setting contact 15 corresponds to a position when the mode switch door 13 is set to a bilevel mode, the fixed contact 21 of the foot mode setting contact 16 corresponds to a position when the mode switch door 13 is set to a foot mode, the fixed contact 21 of the defrost/foot mode setting contact 17 corresponds to a position when the mode switch door 13 is set to a defrost/foot mode, and the fixed contact 21 of the defrost mode setting contact 18 corresponds to a position when the mode switch door 13 is set to a defrost mode. In other words, the actuator turns within a section L between the position of the ventilation mode setting contact 14 and the position of the defrost mode setting contact 18 at both ends and stops at each of the contacts 14 to 18 while turning.
In the above constitution, when the defrost switch 7 is turned on, the microcomputer 2 turns the motor 5 of the actuator 4 in a defrost mode direction and the movable contact 20 rotates with the rotation of the motor 5. When the movable contact 20 contacts the fixed contact 21 of the defrost mode setting contact 18 (the defrost mode setting contact 18 is turned on), this ON signal is input into the microcomputer 2 through the input circuit 22 and the microcomputer 2 stops the motor 5. The mode switch door 13 is thereby set to a defrost mode (a mode for ejecting air from a defrost air outlet).
When the defrost/foot switch 8 is turned on, the microcomputer 2 turns the motor 5 in a defrost/foot mode direction and the movable contact 20 rotates with the rotation of the motor 5. When the movable contact 20 contacts the fixed contact 21 of the defrost/foot mode setting contact 17 (defrost/foot mode setting contact 17 is turned on), the ON signal is input into the microcomputer 2 through the input circuit 22 and the microcomputer 2 stops the motor 5. The mode switch door 13 is thereby set to a defrost/foot mode (a mode for ejecting air both from a defrost air outlet and a foot air outlet).
When the foot switch 9 is turned on, the microcomputer 2 turns the motor 5 in a foot mode direction and the movable contact 20 rotates with the rotation of the motor 5. When the movable contact 20 contacts the fixed contact 21 of the foot mode setting contact 16 (the foot mode setting contact 16 is turned on), this ON signal is input into the microcomputer 2 through the input circuit 22 and the microcomputer 2 stops the motor 5. The mode switch door 13 is thereby set to a foot mode (a mode for ejecting air from a foot air outlet).
When the bilevel switch 10 is turned on, the microcomputer 2 turns the motor 5 in a bilevel mode direction and the movable contact 20 rotates with the rotation of the motor 5. When the movable contact 20 contacts the fixed contact 21 of the bilevel mode setting contact 15 (the bilevel mode setting contact 15 is turned on), this ON signal is input into the microcomputer 2 through the input circuit 22 and the microcomputer 22 stops the motor 5. The mode switch door 13 is thereby set to a bilevel mode (a mode for ejecting air both from an ventilation air outlet and a foot air outlet).
When the ventilation switch 11 is turned on, the microcomputer 2 turns the motor 5 in a ventilation mode direction and the movable contact 20 rotates with the rotation of the motor 5. When the movable contact 20 contacts the fixed contact 21 of the ventilation mode setting contact 14 (the ventilation mode setting contact 14 is turned on), this ON signal is input into the microcomputer 2 through the input circuit 22 and the microcomputer stops the motor 5. The mode switch door 13 is thereby set to a ventilation mode (a mode for ejecting air from a ventilation air outlet).
However, according to the above constitution, when foreign matters in the casing adhere to the surface of the fixed contact 21 or the surface of the movable contact 20 or when a contact fault occurs, an ON signal from the mode setting contact cannot be obtained. As the result, the actuator 4 malfunctions and such a trouble that a foot mode cannot be obtained in winter occurs.
To eliminate the above trouble, in the conventional air conditioner, as shown in FIG. 14, when it is judged that the actuator 4 of the mode switch door 13 is out of order and either one of the defrost mode setting contact 18, the defrost/foot mode setting contact 17, and the foot mode setting contact 16 is turned on, the mode switch door 13 is automatically set to a defrost mode, and when either one of the ventilation mode setting contact 14 and the bilevel mode setting contact 15 is turned on, the mode switch door 13 is automatically set to a ventilation mode, thereby insuring the minimum air conditioning power.
To set a ventilation mode when the contacts of the actuator 4 are out of order, when the actuator 4 is kept turning in a ventilation mode direction (counterclockwise) for a predetermined time in FIG. 13, the mode switch door contacts the wall of an unshown duct, thereby stopping the actuator 4 at a ventilation mode position.
To set a defrost mode when the contacts of the actuator 4 are out of order, when the actuator 4 is kept turning in a defrost mode direction (clockwise) for a predetermined time in FIG. 13, the mode switch door 13 contacts the wall on the opposite side of the above unshown duct, thereby stopping the actuator 4 at a defrost mode position.
A stepping motor actuator having no setting unit 19 which comprises the contacts of the actuator 4 as shown in FIGS. 12 and 13 may be used as the actuator. When such a stepping motor actuator is used to control the mode switch door 13, the control unit does not require a circuit corresponding to the input circuit 22 as shown in FIG. 12. For instance, the amount of rotation of the stepping motor actuator is controlled by controlling the drive circuit with the microcomputer, whereby the position of the mode switch door 13 is controlled.
However, when the actuator 4 having the setting unit 19 comprising contacts is used, air conditioning in a ventilation mode or a defrost mode can be achieved in the case that the contacts 14 to 18 are out of order. However, other modes, i.e., bilevel mode, foot mode and defrost/foot mode, cannot be obtained, leaving an uncomfortable feel from the air conditioning.
When a stepping motor actuator is used as the actuator, it is impossible to control the position of the mode switch door if some abnormality occurs in the control unit for controlling the stepping motor actuator.